Military land mines, namely, explosive devices which are dispersed upon the earth surface or at shallow depths, are intended to explode and injure or destroy an enemy person or vehicle traversing the surface, when the presence of such is sensed. A common means for sensing such presence comprises a fuse mechanism, or trigger, which responds to the downward force, or pressure, of a person or vehicle traversing the surface of the field, to then detonate the main explosive. Typically, the threshold of fuse action is set sufficiently high, so that a mine is not detonated without achieving its intended purpose. Thus, the threshold force may be set higher than that applied by small animals and other wayward objects, or in the case of anti-tank mines, by human beings.
Of course, military forces desire to remove mines placed by the enemy, in order to breach, or to clear a regular route, over a certain piece of terrain. There is, of course, a need to do the job quickly, often under adverse conditions. After hostilities cease, the military and society as a whole have an interest in mine neutralization, so their pernicious effects are not suffered by civilians seeking to peaceably regain use of the terrain for a useful purpose such as agriculture.
Thus, various means have been developed to neutralize land mines, in particular the pressure sensitive type mines with which the present invention is primarily concerned. In an old way, some expendable or specially reinforced object can be run across the mine field, to apply pressure to the surface sufficient to detonate the mines without consequential adverse effect. However, often times the terrain may not permit such, as the efficacy and cost of the means may not be acceptable. In another approach, chemical explosive charges can be detonated upon or along the surface of the earth. But other than to create a narrow breach through the field, such means is not effective unless the applied explosive is selectively placed in close proximity to the mine, which means the mine must be detected in the first instance. In another common approach, the mine is detected and then individually removed and carried away for disabling or destruction elsewhere. Again a mine has to be first found, both to remove and to avoid injury to personnel and equipment being used to remove other nearby mines. That means the detection means has to be good. For example, detectors capable of sensing changes in magnetic field strength have been long used to find ferromagnetic metal mines. But despite continual exploration of new technologies, it is a continuing problem to find mines, and to improve upon the often slow, tedious and risky work of removing them.
Furthermore, mine designers have resourcefully designed mines to defeat the detection means and to otherwise make them more of a threat. For example, mines may be made of non-metal materials, and the fuses may be configured to only detonate after n excursions of pressure beyond the threshold setting, not to respond to the characteristic pressure wave of a chemical explosive, or only to respond to a certain pressure versus time profile. In particular and with relevance to the present invention, mines may have elastically biased triggers in combination with dampeners, for instance of the kind known in fluidics. They can have the effect of requiring that a pressure to be sustained for at least tens of milliseconds. Thus, the triggers of such mines will resist being detonated by a single surface detonation, which lasts only tens of micro-seconds.
Thus, there is a continuing need for an improved means of countering mines and for making mine fields safe to traverse in an efficient and cost effect manner.